Homopolymers and copolymers of oxazolines and polyphenolic compositions are particularly useful as protective coatings and molding compositions.
Oxazolines are known to undergo ring opening homopolymerization generally in the presence of Lewis acids, inorganic acids and cationic catalysts, such as boron trifluoride etherate. Alkyl trifluoromethane sulfonate or alkyl p-toluene sulfonate will also catalyze oxazoline homopolymerization.
Polymerized bisoxazolines yield materials that tend to be brittle and, therefore bisoxazolines are typically used as co-reactants with diphenolic or polyphenolic materials in order to produce a ductile, chain-extended system. Many of these copolymer or terpolymer polymerizations are catalyzed by alkali or alkaline earth metal cationic complexes, phosphine catalysts and onium salt catalysts.
However, the catalyst or catalyst systems presently known to catalyze oxazoline polymerizations exhibit a variety of disadvantages such as, toxicity, flammability, corrosiveness, moisture sensitivity, irritation and unpleasant odors. Safety hazards can be severe, as some of the catalysts are flammable and precautions must be taken to avoid hazardous systems. For example, onium salt catalysts are known to form protic acids, which can be corrosive. Furthermore, additional precautions must be taken when dealing with moisture sensitive catalysts.
In view of the foregoing discussed disadvantages and limitations that exist with the use of known catalysts, improvements are continuously desired and sought by those within the industry. It was against this background that an alternative catalyst system for producing oxazoline homopolymers and, in particular, copolymers of oxazoline and phenolic resins was sought.